The present invention concerns filters and filter elements (suitable but not necessarily for tobacco smoke filters) containing particulate smoke-modifying additive.
Suitable particulate additives include sorbents (e.g. selected from activated carbon, silica gel, sepiolite, alumina, ion exchange material etc.), pH modifiers (e.g. alkaline materials such as Na.sub.2 CO.sub.3, acidic materials), flavourants, other solid additives and mixtures thereof.
The various prior procedures for manufacturing such filters have suffered from one or more of production problems, problems of control over product quality and uniformity, and problems of machinery wear.